JPS62241340A - Vacum drying processing - Google Patents

Abstract

PURPOSE:To enable a drying process to be performed effectively without deterio rating or damaging a dried material, by heating the dried material, which is rotated at a low speed by means of a turn table, nearly at a normal temperature by using infrared heaters and then replenishing evaporation latent heat of water by its heating so that the drying process of the dried material is performed. CONSTITUTION:A carrier 13 inside a verger 10 is provided with a plural sheets of washed wafers X supported, and placed on a turn table 14 which is driven by rotation at a low speed of 30 rpm or so. And, infrared heaters 15 and 16 are installed up and down inside the verger 10. The upper one is of a suspension type inside the verger, and the lower one is of a mounting type on a base plate 12. The dried material is heated below 40 deg.C, nearly at a normal temperature, by the respective heaters 15 and 16 so that evaporation latent heat of water attached to the dried material is replenished. Thus, because water is sublimated under a vacuum atmosphere and water inside a slit is also vaporised effectively, the wafer is prevented form being deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vacuum drying method suitable for drying a wafer after washing with pure water.

Conventional technology In general, centrifugal separation is used to dry wafers, but the disadvantage is that the wafers are easily damaged by vibrations during high-speed rotation, and that moisture adhering to the inside of the slits of the wafers cannot be completely removed. Therefore, it is desired to develop an alternative drying method.

Conventionally, this type of drying treatment method involves providing a counter electrode that forms an electric field in an airtight chamber that is depressurized to a predetermined pressure, and applying a high-frequency voltage to the electrode to turn the depressurized atmosphere into plasma.
There is a known method of drying the object under reduced pressure by placing the object supported by a predetermined holder in plasma and replenishing the latent heat of vaporization of the cleaning liquid (Japanese Patent Laid-Open No. 51-6756).
No. 8).

Problems to be Solved by the Invention However, in this method, the kinetic energy of plasma ions and electrons that continuously collide with the surface of the object to be dried is partially converted into the latent heat of vaporization of the cleaning liquid, so that the cleaning liquid remaining on the object to be dried can be removed. Although drying can be performed without freezing, when it is applied to drying wafers, it is not preferred because there is a risk of deteriorating the quality of the wafer or forming a super ivy film on the surface.

Means for Solving the Problems In the vacuum drying method according to the present invention, the pressure inside a bell jar containing the material to be dried is reduced to a predetermined vacuum pressure, and the material to be dried, which is rotated at low speed on a turntable, is heated by an infrared heater. The material to be dried is heated to approximately room temperature, and the material to be dried is dried while replenishing the latent heat of vaporization of water.

Function: In this vacuum drying method, the wafer is heated to approximately room temperature to replenish the latent heat of vaporization of the water, and the water is sublimated under vacuum, thereby preventing the water from freezing while remaining on the wafer. Since moisture can also be efficiently evaporated, there is no risk of deteriorating the quality of the wafer even when it is applied to dry the wafer, and since it only rotates at a low speed to heat and irradiate the entire wafer, there is no risk of damaging the wafer. Not at all.

Embodiments will now be described with reference to the accompanying drawings.

The drying apparatus shown in Fig. 1 is for vacuum drying wafers together with carriers after washing with pure water in a clean room.
The bell jar 1o is configured to be able to reach a degree of vacuum of approximately 5×10 Torr. The inner surface of the main body is formed into a smooth surface by puffing and electrolytic polishing, and as shown in FIG. 2, it is mounted so as to be able to be lifted up from a base plate 12 by an air cylinder 11 installed on the body side. Inside this bell jar 10, a plurality of wafers X cleaned with a carrier 13 made of Teflon or the like is supported and accommodated.
The carrier 13 is placed on a turntable 14 which is rotated at a low speed of about 30 rpm. Further, two infrared heaters 15 and 16, upper and lower, are installed inside the bell carrier 10. The infrared heaters 15, 16 can be made of tungsten or the like, and the upper part can be suspended in a bell jar, and the lower part can be constructed by a mold for installing the base plate 12. For example, when the object to be dried is an 8-inch carrier 13° wafer X, a power of about 200 W can be used. Replenishes the latent heat of evaporation of moisture attached to objects.

This drying processing apparatus can perform vacuum processing of the bell jar 10 and discharge processing of condensed water using the circuit system shown in FIG. In the circuit system, 2o is the main valve, 21.22 is the leak valve, 23 is the filter, 24 is the trap, 25
26 is an auto drain valve, 26 is a refrigerator, 27 is a water cooler, 28 is an oil rotary pump, and 29 is an oil cleaning device.

In this drying processing equipment, the lifted bell jar 1
0 manually or by a robot to insert the material to be dried into the turntable 14 which is positioned and stopped within the main valve 20. The leak valve 21 is opened and the leak valve 22 is closed to start evacuation. This exhaust gas is discharged outside the clean room via a through duct. When the vacuum pressure reaches a predetermined pressure, for example, when the object to be dried is an 8-inch carrier or wafer, the vacuum pressure is 46 to 45 Torr as shown in Fig. 3.
When the temperature reaches about r, the upper and lower heaters 15 and 16 are activated. Since each of the heaters 15 and 16 has a power of about 200 W, the temperature of the material to be dried does not rise above 40°C. Further, the heating by the heaters 15 and 16 is applied uniformly to the entire object X by rotating the turntable 14 at a low speed of about 30 rpm. When the internal pressure of the bell jar 10 reaches approximately 30 Torr in this state, the carrier 13. The moisture adhering to wafer X starts to evaporate, and the evaporation occurs quickly even if it adheres to the inside of the slit of wafer X, causing the internal pressure of the bell jar to rise to 2 Torr.
When it reaches about r, it is almost completely finished. Since carrier 13 and wafer Object X does not freeze even if moisture remains attached to it.

The evaporated moisture is transferred from bell jar 10 to trap 2.
By separating the frozen water and the heat-generating low pressure, only the heat-generating low pressure is sent to the refrigerator 26 and returned to room temperature and high pressure in the cooler 27. Thereafter, the normal temperature and high pressure is returned to the trap 24, and the frozen water accumulated in the trap 24 is heated and melted by this normal temperature and high pressure, so that it can be discharged from the drain valve 25 to the outside of the machine.

When the water vaporization of the material to be dried is completely completed, the heaters 15 and 16 are closed, and at the same time, the main valves 20 and 20 are closed. By closing the leak valve 21 and opening the leak valve 22, the internal pressure of the bell jar 10 is increased. At this time, since the filter 23 is connected to the leak valve 22, clean air is supplied to the bell jar 10. bell jar 1
When the internal pressure of 0 reaches atmospheric pressure, the bell jar 10 is lifted up and the material to be dried X is taken out, thereby completing the drying process.

As described above, according to the vacuum drying method of the present invention,
Since the latent heat of evaporation of water is supplied to the material to be dried using an infrared heater that heats it to approximately room temperature, it becomes possible to perform the drying process efficiently without altering or damaging the material to be dried.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the internal structure of a bell jar that implements the vacuum drying method according to the present invention, Fig. 2 is a system diagram of the vacuum of the bell jar and condensed water treatment, and Fig. 3 is a diagram showing the vacuum pressure and condensed water treatment of the bell jar. It is a graph showing the relationship between water vaporization and evaporation. 10: Bell jar, 14: Turntable, 15.16
:Infrared heater.

Claims (1)

[Claims] The inside of the bell jar containing the material to be dried is reduced to a predetermined vacuum pressure, and the material to be dried, rotating at low speed on a turntable, is heated to approximately room temperature with an infrared heater, and the latent heat of vaporization of water is replenished by this heating. A vacuum drying method characterized in that a material to be dried is dried.